1. Technical Field
The present disclosure relates to a microscope apparatus.
2. Related Art
In general, there are two types of microscopes used in the field of biological research. One is a fluorescence microscope for fluorescently staining a specimen. The other is a microscope for observing a transmitted light, a diffracted light, and/or a reflected light from a specimen without fluorescently staining the specimen. As these microscopes, a bright field microscope, a phase contrast microscope, a differential interference microscope, and the like are known.
FIG. 19 is an explanatory diagram illustrating a configuration of a typical phase contrast microscope disclosed in JP-A-5-333272. As illustrated in FIG. 19, the phase contrast microscope includes a light source 1, a condenser lens 2a and an imaging lens 2b constituting an optical system 2, an aperture diaphragm plate 3, and a phase plate 4. A transparent observation object 5 is supported on a specimen table 6, and arranged between the condenser lens 2a and the imaging lens 2b. In this drawing, an imaging plane 7 is arranged above the phase plate 4.
The aperture diaphragm plate 3 is configured to be able to change an illumination light from the light source 1 to a squeezed light having a predetermined pattern such as a ring slit shape.
The phase plate 4 includes a transparent plate 4a and a phase control film 4b. The phase control film 4b is formed on the transparent plate 4a to have the same shape as an opening of the aperture diaphragm plate 3. The phase control film 4b causes a delay (or advance) in phase of light transmitting therethrough, and reduces the amount of transmitted light. The aperture diaphragm plate 3 is disposed at the front focal position of the optical system 2, while the phase plate 4 is disposed at the rear focal position.
Light emitted from the light source 1 is first passed through a light transmitting portion of the aperture diaphragm plate 3, and formed into a ring-shaped light. The light is collimated to a parallel light by the condenser lens 2a, and then transmitted through the observation object 5. The transmitted light is passed sequentially through the imaging lens 2b and the phase plate 4, and focused on the imaging plane 7.
When the observation object 5 is homogeneous with no irregularities on its surface, the illumination light narrowed down to the ring shape by the aperture diaphragm plate 3 is transmitted through the observation object 5, passed through the phase control film 4b of the phase plate 4, and projected directly on the imaging plane 7 as a direct light (S wave).
On the other hand, when another object 5a is stacked on the observation object 5, for example, it may cause a difference in refractive index or irregularities on the surface of the observation object 5. In such a case, the light is diffracted when passed through the area of the observation object 5 where the object 5a is located. The diffracted light (D wave) is transmitted through the area of the phase plate 4 excluding the phase control film 4b. Further, the D wave shifts in phase with respect to the S wave.
The phase shift changes depending on the thickness of the object 5a, and the difference in refractive index between the area of the object 5 where the object 5a is present and the other area. When the refractive index difference is small and the object 5a is thin, the phase shift is approximately λ/4. Here, the aperture diaphragm plate 3 is disposed at the front focal position, and the phase control film 4b of the phase plate 4 is disposed at the rear focal position. Thus, the S wave always passes through the phase control film 4b. 
Therefore, by shifting the phase (wavelength) of the light passing through the phase control film 4b in the delay or advance direction by λ/4 with respect to the D wave, and setting the amount of the transmitted light to almost the same as the amount of the diffracted light, the direct light and the diffracted light interfere with each other and therefore a difference in brightness in an image formed on the imaging plane 7 is generated. When the phase is shifted by the phase plate 4 in the advance direction, a positive contrast is displayed on the imaging plane 7. When the phase is shifted in the delay direction, a negative contrast is displayed.
FIG. 20 is an explanatory diagram illustrating a configuration of a typical fluorescence microscope disclosed in JP-A-5-150164. As illustrated in FIG. 20, light emitted from a light source 11 (e.g., a mercury lamp) is condensed by a collector lens 12.
An interference filter 13 functions as a transmission wavelength shifting filter. The interference filter 13 is rotatably held about an axis vertical to an output side optical axis of the collector lens 12. On the output side of the interference filter 13, an aperture diaphragm 14, a field diaphragm 15, an excitation filter 16 having a predetermined transmissivity, and a dichroic mirror 17 having a predetermined transmissivity are arranged in this order.
The reflected light from the dichroic mirror 17 is emitted to a specimen 20 placed on a vertically movable stage 19 via an objective lens 18. Two kinds of fluorescent lights emitted from the specimen 20 are guided to the dichroic mirror 17 through the objective lens 18 again.
An absorption filter 21 having a predetermined transmissivity and a beam splitter 22 are disposed on the exit side of the dichroic mirror 17. The beam splitter 22 is removably disposed in an optical path to switch the optical path to the observation system or photography system as appropriate.
An eyepiece optical system 23 is disposed on the observation system optical path side of the beam splitter 22. An eyepiece lens for photography 24 is arranged on the photography system optical path side.